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TLOF Centre Point (aimingPoint)
PANS-AIM requires the centre point of the TLOF to be provided including its elevation and geoid undulation.
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In AIXM, only the aiming point of a TLOF can be coded. Is the aiming point the same as the centre point of a TLOF? According to ICAO Annex 14, Volume II,
This definitions give the impression that the aiming point is not the centre point of the TLOF. Currently in AIXM, it is not possible to define the two different points for a TLOF. Anyhow, it seems that the relationship hasAimingPoint and the property TLOF.aimingPoint is not correct. It should be rather hasCentrePoint and TLOF.centrePoint. Also, an aiming point may be independent from a TLOF and may also be marked and lighted. It seems that currently aiming point is not covered by AIXM 5. The workaround is to code that information in a Note. |
A workaround is to code the centre point of the TLOF using the ElevatedPoint class linked by the hasAimingPoint relationship.
The ElevatedPoint class provides also dedicated attributes for elevation and geoidUndulation.
In addition the horizontal and vertical accuracy defined by PANS-AIM may be coded using the horizontalAccuracy and verticalAccuracy attribute.
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| In case an aiming point and a centre point shall be coded for the TLOF, the actual aiming point has to be coded as Note. |
TLOF Dimension (length & width)
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The TouchDownLiftOff.width is the declared transversal extent of the TLOF.
PANS-AIM also defines accuracy values for the TLOF length and width.
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| For both attributes a dedicated attribute to provide accuracy is missing in AIXM 5. |
As a workaround, the accuracy value for the length and width may be encoded as note annotation for the corresponding property.
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| title | Open Question circle TLOF |
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In addition the extend of the TouchDownLiftOff may be coded using the Surface class.. In case of a rectangular shape the defined extend (by a set of points with latitude longitude information) shall be consistent with the provided length and width values.
In many cases the shape of a TLOF will be a circle rather than a rectangular. In such case the length and width may not be coded (although required as minimum data for the AIP data set). In such cases only the extend shall be coded using the corresponding gml element for a circle (see document 12-028_Use_of_GML_for_aviation_data-2.pdf).
Surface
For the TLOF, PANS-AIM requires to provide the surface type.
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| Identifier | Data Encoding Rule | Justification | Data Verification Rule (UID) | Remarks |
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| TLA-101 | The TouchDownLiftOff.designator attribute is mandatory. | Minimum AIP data set | TBD | |
| TLA-102 | The TouchDownLiftOff.aimingPoint attribute is mandatory. | Minimum AIP data set | TBD | The aimingPoint property is used to actually code the centre point, see also AIXM 5.1(.1) issue above. |
| TLA-103 | The TouchDownLiftOff.length attribute is mandatory unless an extend is coded. | Minimum AIP data set | TBD | Actually, PANS-AIM requires the length and width as part of the minimum AIP data set. Many TLOF will have rather the shape of a circle. In such cases the length and width attribute do not provide the correct information, but the Surface class shall be used to encode the correct extend of the TLOF. Also, if a a rectangular is encoded as extend for the TLOF the length and width attribute are not needed but may be provided in addition for publication purposes. |
| TLA-104 | The TouchDownLiftOff.width attribute is mandatory unless an extend is coded. | Minimum AIP data set | TBD | see rule TLS-103 |
| TLA-105 | If a value for the TouchDownLiftOff.length attribute is provided a Note for the TouchDownLiftOff with propertyName equal-to 'length' shall be coded to provide the corresponding accuracy. | Minimum AIP data set | TBD | |
| TLA-106 | If a value for the TouchDownLiftOff.width attribute is provided a Note for the TouchDownLiftOff with propertyName equal-to 'width' shall be coded to provide the corresponding accuracy. | Minimum AIP data set | TBD | |
| TLA-107 | For TouchDownLiftOff the SurfaceCharacteristic.composition attribute is mandatory. | Minimum AIP data set | TBD | |
| TLA-108 | The position given by ElevatedPoint must be plausibly close (less than 20 KM) to that of the ARP of the related AirportHeliport. | EAD | TBD | |
| TLA-109 | ElevatedPoint.geoidUndulation may be specified only if ElevatedPoint.elevation has been specified. | EAD | TBD | |
| TLA-110 | The related Runway should be related to the same AirportHeliport as the TouchDownLiftOff. | EAD | TBD | |
| TLA-110 | If both a width and length and also an extend is coded the data have to be consistent (i.e. the points defined by the extend have to match with the values of the length and width). | Data consistency | TBD |
Coding Examples
TBD in the scope of Coding examples can be found in the DONLON AIXM AIP data set file:
| No. | Description | XPath Expression |
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| TLA-EX-01 | TLOF (rectangular shape defined by with length/width and extend) | //aixm:TouchDownLiftOffTimeSlice[@gml:id ='TLA_EADH_TLOF] |